In general, a vehicle air suction system includes an air filter which filters foreign substances from intake air, a throttle body which has a throttle valve for regulating an amount of intake air, and a surge tank which has an intake manifold for distributing air to each cylinder of an engine.
In the air suction process using the air suction system, the intake air filtered by the air filter is introduced into the surge tank via the throttle body depending on whether or not the throttle valve is opened or closed. Subsequently, the intake air is distributed from the surge tank to the intake manifold communicating with each cylinder to be mixed with fuel injected from an injector, and then is introduced into the cylinder for combustion.
In addition, the throttle body includes a coolant passage for freeze prevention. That is, the throttle body has a structure for preventing freezing by supplying coolant, the temperature of which increases while passing through the coolant passage in the engine, to the throttle body such that the coolant is circulated in the coolant passage provided in the throttle body, and by increasing the temperature of the throttle body.
However, the throttle body having the coolant passage therein is supplied with coolant, the temperature of which is increased while passing through the coolant passage in the engine, even during warm weather even when there is no concern about freezing. Accordingly, the temperature of the throttle body increases. For this reason, the temperature of intake air passing through the throttle body may be increased.
That is, the conventional method for supplying coolant to the coolant passage in the throttle body may not prevent the temperature of intake air passing through the throttle body from being increased, which may lead to deterioration of the efficiency of the engine, such as an ignition timing delay, due to the increase in temperature of intake air.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.